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  1. #1
    Senior Member Tinman's Avatar
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    Default Engine blocks 308

    I am looking to rebuild the bottom end of my 308 in a ski boat. I currently have a red motor which I think is a 1969 block from a HG but not certain. I have not had it pulled right down before so I dont know how oversize the bore is but being so old I would not be supprise if it is 60thou over allready. Generally in boats they dont like to go more than 40thou as the cooling system is open circuit and picks up cold water so there can be faily rapid temp flutuations. I would also be looking to build the bottom end before I pull the motor out anyway. So I need a few Questions answered before I start looking for a block.

    1. What differences are there in Red, blue and black motor bottom end?

    2. Are the engine mount bolt patterns the same on all?

    3. What is the difference in the timing gears? For marinising an adapter for drive fits on to front of crankshaft where harmonic balancer normally goes.

    4. Is the timing cover the same on all? (bolt pattern) This is crittical for marinising parts as dog clutch bolt up to front of motor where timing cover goes.

    5. Is the fuel pump set up the same on all 3?

    6. Is the oil pump the same on all 3?

    7. Is there any difference in the crankshaft between them? Other than HQ neoprene oil seal models and spiggot depth with SBC/Aust bell housing bolt patterns and 304ci motor shorter stroke.

    7b. Is the flywheel bolt patter the same on all? eg one offset.

    8. Why if you put black heads on red motor do you need to change cam and push rod? Is this correct? I have read a few bits and pieces on this site and others and there seems to be a bit of conflict here.

    9. Are the camshaft and lifters the same in all 3?

    10. Do some or all black motors have four bolt mains??? Are the cranks the same in these?

    11. Are the conrods the same in black blue red?

    I am thinking a long the lines of getting a black motor with the 4 bolt mains (if this is not a myth) and building it up with my red motor top end including cam lifters and timing gears. So any info would be great. I would also consider stroking it to 355. This is going to be a medium term project.
    Cheers Tinman

    Jack of all trades master of none

  2. #2
    casual poster wedgemotors's Avatar
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    Smile

    I think all carbed 308s are much of a muchness with the exception of some head to intake patterns, its only once you got to VN onwards that parts dont interchange I cant say for sure about this & no doult if im wrong I will quickly get corrected, have you got another cyl block yet?
    I spent most of my money on fast cars and loose woman, the rest I just wasted.

  3. #3
    Senior Member Tinman's Avatar
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    Quote Originally Posted by wedgemotors
    I think all carbed 308s are much of a muchness with the exception of some head to intake patterns, its only once you got to VN onwards that parts dont interchange I cant say for sure about this & no doult if im wrong I will quickly get corrected, have you got another cyl block yet?
    It is the VN onward I am probably looking at (Black motors). I have read a few things that talk about changing cams and timing gears with the black motors and ealy heads but it was not real clear as to for what reason. I am pretty ok with all the head stuff. The will all bolt on all the blocks but the inlet manifold has to match the heads. (That is the easy part). And the exhaust manifolds.
    Cheers Tinman

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  4. #4
    254RWHP boat anchor EVL253's Avatar
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    vn heads yes different cam manifolds intake and exhaust are needed

    black motors come out in vk's but are the old style heads

    all timing cover bolt patterns are the same as is the oil pump and fuel pump bolt up's.same for starter motor.

    in short most things are much the same just minor details that changed
    I love Prius drivers cause I need their share of the fuel supply!

  5. #5
    HDTCQ mechanic #2 skidmarx's Avatar
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    yes, most things are the same, except u have turbo or aussie blocks, black motors came out in VK's yes, but from memorys the walkinshaw and VNgrpA motors were also called black motors, and from memory only the grp A motors had 4 bolt mains

    to run VN or later heads yes u do need to change cam, lifter and rods and all that as there efi heads and if i remember correctly arnt exactly the same as older heads (valve train wise)

    as far as i can remember the bottom ends are all the same except that as the years went by they obviously found/made better parts, so my theory is the newer the motor the stronger it will be in stock form, although im sure everything say from a vk 308 black motor will bolt strait into a HG red motor or vice versa, personaly i love the VK black motors, and wouldnt build on anything newer
    100% pimp factor, long live the VK
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  6. #6
    bad tempered old c@&t wabbit's Avatar
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    VN and later blocks had stronger webbing between the main caps.

    if your block is a 1969, it will be a trimatic pattern block. it will also be a neoprene seal type block and will have weaker structure around the bellhousing dowels.

    you really can't beat the VN and later blocks for strength. and they are usually in better condition, due to being younger blocks.

    and if the heads will interchange, as long as the rest of the valvetrain is matched, like some of the earlier posts mentioned.

    so, in order
    1. red, blue and black- no basic difference from later HQ rope seal blocks to the VL blocks. excluding the Walkinshaw blocks. up to somewhere in the HQ series, the blocks were weaker on the bottom end. VN and later they were stronger. VSIII/VT blocks had higher lifter bores for roller lifters. there were some 4 bolt main blocks made, usually for the HSV stable. also, VS(?) onwards were clearance for stroker cranks.

    2. the earlier (HG?) blocks had a different engine mounting pattern, but the only difference was in the engine mounts used

    3. as per el skidmarx

    4. timing cover bolt patterns are identical thoughout the range.

    5. efi engines have an electric fuel pump and the timing covers for these have no provision to mount the mechanical pump. all others identical

    6. oil pumps identical. oil pickups differ depending on sump used. i assume yours is a custom marine sump. interchangeable, anyway

    7. i think you've pretty much hit the nail on the head, there

    7b. pass

    8. as per some of the others, EFI heads on an older block, you need cam, intake and exhaust manifold change. pushrods should be fine- upgraded for strength, of course

    9. as per last. valve arrangement is different. lifters are identical until roller lifter engines

    10. 4 bolt mains exist. i have seen them for around the 2k mark. that's probably a fair price if you need the numbers, but you could buy a virgin bore, late model block and get it converted to 4 bolt mains for less.

    11. conrods. you have large X and small X rods. what are they ? L34 and something to do with VK engines rings a bell. VN and later rods are the most plentiful and cheapest. i reckon they're close to, if not the strongest.


    so, your cheapest option would be a later block. VN and later would be ideal. VS and laster for the stroker clearancing, but it's not a big job to clearance any block yourself.

    if your red motor top end is in need of a rebuild, you might be better off looking for an EFI top end. Price around. these things are getting cheaper by the day
    If a man says something in a forest, and his wife isn't there to hear him................is he still wrong?

  7. #7
    Senior Member Tinman's Avatar
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    Some great info thanks guys.


    Wabbit, I am a bit of an old timer 70's 80s erra. I have had a fair bit to do with red motors but nothing newer. With the conrods the L34's rod were out of the Torana A9X and a few other High performace models and are heavier with larger bolts in the big end caps being the main thing. What is the VK thing?

    This cam issue is still a bit confussing.

    It seems that the cam is an issue when it come to the EFI models. Is it that the EFI requires different valve timing to the natural aspiration or is it that there is a difference in the valve train?

    Is the rocker ratio the same (1.65:1 for red motor)?

    Are the valves sitting higher or lower (hence longer/shorter pushrods)?

    If not one of these what is it that is different?

    I have a set of bathurst spec heads (no EGR) and YT5033 roller rockers that I want to use (standard ratio 1.65:1). As much as the newer heads have good specs similar to what I have and are better ported, if I go that way I would have to change my marinised mannifolds and stainless exhausts which would not be much change from $1000. As well as this they have been putting the new motors in some of the new boats with the EFI and computers. They are now going away from it because the computers are not programed to suit a boat. Every time the prop slips in the water they do the electronic traction control thing and run erratic and uneconomical.

    So the Question is can I use my existing cam and lifters running my heads?

    When did they start putting in the roller lifters? I would assume longer lifters and shorter push rods and roller rocker of course.

    Not a 100% because I have had the tape measure out to measure it yet but i think its the turbo bolt patern on my existing block. That is the least of my worries, so long as they still make both patterns it is insignificant. The thing that makes me think it a HT block is it has no dampner on the timing chain and no facility to bolt on in. Every other 308 I have touched has had one. I am guessing it would have had the same Saginaw gear box and bell housing as the 307SBC in the HT.

    The four bolt mains are not essential but an option I want to explore. I just want a solid bottom end. It is not like a drag car @ 8000RPM. Aiming to get about 5500RPM but sustain that for long periods.

    The engine mounts are alloy castings that bolt to the stringers in the floor. So long as the bolt pattern hasnot changed there is no problem.

    So long as the timing coverbolts alignment is the same there is not an issue there because whether I stick whit how the setup is now or put in a dog clutch the marinising gear bolts up here and the fuel pump.

    I will look at the stroker idea a bit later on, but it is another option I wish to explore along with the SBC 350ci. Checking out all my option and comparing costings.

    So thanks again for your imput guy/girls
    Cheers Tinman

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  8. #8
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    If you're really interested in knowing what your block is originally from, post up the engine prefix and the date casting and I'll let you know.

    The date casting is on the top front of the block just near the water pump.

    It will be a 3 or 4 digit alpha-numeric (numbers and letters) code and is cast (raised up) and not stamped.

  9. #9
    bad tempered old c@&t wabbit's Avatar
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    your major issue with the EFI is the arrangement of the valves.

    instead of the IEIEEIEI formation, they have IEIEIEIE.
    obviously, they must have a cam to suit, or all sorts of weird, metallic noises happen.

    your existing cam and lifters are fine with any pre-EFI heads.
    rockers ratios are the same. peshrod lengths should be similar, but decked blocks, shaved heads, recessed/new valve seats, ground cam, different thickmess head gaskets all play a part in what the pushrod length should be.

    as Munromad said, post up the engine number prefix and casting code and we should be able to nut out exactly what you've got.

    for the turbo/ trimatic question, see here
    308 prefixes

    scroll down for pictures
    If a man says something in a forest, and his wife isn't there to hear him................is he still wrong?

  10. #10
    Senior Member Tinman's Avatar
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    Quote Originally Posted by wabbit
    your major issue with the EFI is the arrangement of the valves.

    instead of the IEIEEIEI formation, they have IEIEIEIE.
    obviously, they must have a cam to suit, or all sorts of weird, metallic noises happen.

    your existing cam and lifters are fine with any pre-EFI heads.
    rockers ratios are the same. peshrod lengths should be similar, but decked blocks, shaved heads, recessed/new valve seats, ground cam, different thickmess head gaskets all play a part in what the pushrod length should be.

    as Munromad said, post up the engine number prefix and casting code and we should be able to nut out exactly what you've got.


    for the turbo/ trimatic question, see here
    308 prefixes

    scroll down for pictures

    Gotta love them metalic noises. Or not. One of the stellite valve seat in my mates 350 let go recentlys ucked the pieces back up through the inlet manifold and back through every pot. Salvagable parts SFA.

    That makes sense. Its quite elementry Watson. I sort of thought that the other day looking at a picture of the exhaust ports but it did not show the valves.
    The YT5033 rockers are adjustable should not be a problem.
    Cheers Tinman

    Jack of all trades master of none

  11. #11
    The Midnight Barber nath_korn's Avatar
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    If its any help, i recently rebuilt my red 308, I changed over to vn heads because they flow something like 400 hp from the factory. They bolt straight onto the pre-efi block. I had to change the cam, lifters to suit the cam, pushrods, roller rockers were interchangeable, inlet manifold, and extractors.
    I still wanted to run carby tho so i used a inlet manifold from harrop ( torque-power also make them) to suit a carby on vn heads. U wont need 4 bolt mains if u want to sustain 5500 rpm, 2 bolt should be adequate. And the boys are right the efi parts are far stronger than the pre efi stuff, Iv heard of A9L rods holding up to 8000rpm same with standard cranks and the blocks are far better, especially if ur wanting to go with a 355.
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  12. #12
    Do you ever leave? WB5LTR's Avatar
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    useless input here

    EFI would be cool. The local auto elec has a EFI 355 in is speed boat. The build has been going on for a while but **** its preeety awesome to look at.

  13. #13
    Newbie GRMBLZ's Avatar
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    i'd just buy a VN-VS bottom end, and chuck all your exsisting manifolds, heads carb etc on it. and find a cam that suits 5500rpm

  14. #14
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    grmblz problem with that is bolting up his prop drive bolt holes probably won't line up

  15. #15
    Senior Member Tinman's Avatar
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    Prop drive not a problem. An adapter bolts up with the fly wheel using longer bolts. A drive shaft about 800mm long then bolts to that and into the "V" drive at the other end. I have been watching around for a cheap 304 VU pefix motor to work with but not in any hurry. I have bid on a couple on EBAY but the went beond what I am prepared to pay. Espescially if it is not local as there is freight cost aswell. I still have not made the final decision on which way to go Holden Stroker 355ci or Chev 350ci 330HP crate motor. My mate the one that had the metalic noises put the 330HP chev in his. My 308 is not running too bad at the moment so inless it gives up the gost I will just keep my eye out for what is on the market.

    As for putting in a big cam to get more revs this can be a problem because of the dog clutch. Although it is refered to as a clutch it is realy just a gear that is either in or out. It must be able to idle below 700RPM in neutral to get it into gear but not stall when it is droped into gear and loaded. If the cam is too lumpy this can be a problem. It also needs to have good low down torque off the mark from idle to pull two skiers out of the water.

    The EFI is an interesting concept but so far not the most successfull thing in boats. The has been quite a few built over the last few years with EFI but many are now going back to carby. From what I understand they are not anywhere near as economical because the computer is not designed for a boat and constantly trying to compensate for the propellor slip in the water or atleast this is what I have been lead to believe by a marine mechanic that works on a lot of ski boats.
    Cheers Tinman

    Jack of all trades master of none

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