dereknkathy

L29s give 9 to 1. fine for iron heads 87 octane. your pistons are flat. domes don't work with L29 heads. they have the heart shape that has a flat surface between the valves- right where the domes are biggest. so 10:1 is not a realistic option. also a little less total timing. 30 degrees full tops. and of course you bought the only good intake for peanut heads. if still new in box, you may wanna see if the can exchange for oval RPM or similar...that is if you go with ovals instead of peanuts...

demax990

The twr 2399 pistons that I got are 13.8 cc Dome, with single valve relief not flat top. so are you saying that the vortec heads will not work with my pistons?.

dereknkathy

I thought 2399 were flat forged. You can grind down the comb chamber to clear the domes. And i think that the l29 is about the only large oval gen 5-6 head.

demax990

Ok good so I can still use the vortecs but cut to cut the chambers is that correct. I have a machinest at work and a mill and the rest of the goodies should be able to do it. You got any pictures

Budman II

iTrader: (1)

demax, there are a lot of people on here who are running the Mk IV heads on Gen V blocks. You just have to use the correct head gaskets. If you do a little searching on this forum, you should be able to find the ones that you need, or give Fel Pro or Cometic a call.

Sounds like a lot of work to grind out the chambers on a set of Vortec's to try to get the piston domes to clear. And after all that, you have to cc the heads to make sure the chambers are all the same size. Are we sure that there is no chance of hitting any water jacket in that area? If those are very small domes, why not just have them milled off by the machinist? This could be done with more precision than trying to hand grind the heads, and I am guessing (hoping) that you are going to have the reciprocating assembly balanced anyway.

After you spend the $200 on those heads, how much are you going to have wrapped up in springs, retainers, and keepers to match the cam? What about a worst case scenario of having to replace guides? I found out the hard way that setting up a set of cast iron GM heads for a high performance boat engine that you want to live for more than a couple hundred hours costs a lot of money, and before you know it you start to approach the cost of a good set of aftermarket heads that flow much better. Sit down with a pencil and calculator and figure up your outlay before buying the heads. Otherwise you might end up with a couple of sets of cast iron GM heads sitting in your garage like I did.

Budman II

iTrader: (1)

I wouldn't try to go 10:1 on a cast iron head motor - stay around 9:1 - 9.25:1 for safety. You never know when you will be stuck with no other alternative than questionable gas.

Also, the fast-burn chambers used on the Vortec heads generally take less initial timing than the old 1960's chamber design of the earlier heads. The advice of staying around 30* total timing is probably pretty valid.

demax990

I don't know what I want to do. I would love to put on a diffrent set of heads. I have read tones on the mkiv heads on the gen 5 blocks some say it works others say it does not. The vortec heads look brand new the owner said he swaped them with aluminum ones and that the heads only have 40,000 kms on them. I was just hoping to grind the heads so that everything clears. Has anyone does this? I don't want to touch the pistons as one day I want a set of aluminum heads and don't want to do a tear down. If I get 200 hours on this engine I will be more than happy. For me that is about 5 years of boating. The heads are 200 I need studs for the rockers that is 100 unless I find used and a set of springs for my hyd roller set up maybe 400 to 450 total and that is in Canadian funds. Someone will say well I can sell you my 088 for 500 and be better off but have you seen the price of our dollar 500 us funds is like almost 700 Canadian put shipping ontop and I got me a set of 088 for a grand with 500 hours on them and still need springs. There is not a lot of performance boats where I am and if they are they got a 5.0 or a 5.3 in them heck some people here have threw hull exhaust with a 4.3 v6

dereknkathy

forget the vortecs. they are a come-up if you have a flat-pistoned stock bottom end. they have the fancy chamber that burns quik and requires less timing. nice med perf head...just like the peanut. they flow little better than a peanut. of course 049 and 781 don't flow that much better than a peanut til you port them and up-valve them till they are rect port heads with smaller ports. your bottom end is a mag now. the domed pistons require a larger chamber for fit AND compression ratio. now you want 118 cc chambers. the ski jump in the vortec intake also improves swirl and combustion. but costs airflow at higher rpms. sounds kinda like a peanut doesn't it? your peanuts are paid-for and you apparently have the matching intake. the vortecs are about half the price of 188 gen 6 rect heads. and i assume the peanuts are a known-good item? save the money for a head worth that bottom end you built and drive the paid for peanut set-up.

demax990

Ya I am just going to use the peanut ports. Got suggestion for a better cam for the peanut ports

I just re read my older posts a gm 454/502 ho cam I beleve

demax990

maybe a set of 1.8 rockers would help? I know jd has a set for sale in swap shop