FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: CV355 on June 19, 2019, 07:17:22 AM
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While chasing a valve cover gasket leak, I discovered that the previous owner of my 428 decked the CJ heads (hence the high CR), and the intake/head plane has a pronounced step. Instead of spending money to machine the intake down to match the head plane, I'm considering pulling the heads and replacing them with Trick Flow 175 heads and a Track Heat intake. That way, I can correct the compression ratio down a bit and have a known starting point. In one of my other threads, I asked about the streetability of the Lunati cheater cam that I have, and was told basically "leave it in, it's fine."
What are your thoughts on this combo? Does anyone have experience with the TF heads for the 428? Anything else I should consider?
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The TFS heads may actually even raise your compression ratio. They are a hair under 70cc as shipped.
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As long as I can run it reliably on 93, I'm ok with 70cc. If I pull the existing heads, I'll have to volume test to see how much was actually taken off when they were decked. My guess is that they were going for stock class limit, which I believe was 68cc. As long as I'm not increasing CR, I'm ok.
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I was going to say that aluminum heads can tolerate a bit more CR, but then I remembered that Car Craft (or Hot Rod) did some testing on that and found it to be bogus. Not much difference between iron and aluminum for octane tolerance.
If you had any issue, you could retard the cam 2~4 degrees, but that also kills bottom end some so - nothing is free.
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Octane tolerance - assuming compression ratio, ignition timing and valve timing remain constant - is a function of combustion chamber design. Newer heads, which are most often made of aluminum, will have a more modern updated combustion chamber design. Hence the oft repeated story of aluminum heads being able to handle more compression.
You need to cc your existing heads to determine if the alternate will lower - or raise - your compression ratio. Your choice of any newer head will no doubt improve performance. That big single plane intake will, however, take any low end torque and "kick it where it counts". Might be better served with another choice there - whether one of the older small single planes or even a dual plane RPM or Blue Thunder.
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Yes, agree - should have thought of that. The AFD heads I put on the 393C run rings around the visual equivalent of the iron 4V heads from the 70s'. And all I did was add the valve train and wash them, then bolt them on the motor.
Now all that said, I run a Funnelweb 4V intake on that engine and there is no port match. The intake sits a tad high. The AFD and Funnelweb ports are very similar with the Funnelweb aimed at "stuffed" 351C 4V style ports. Hasn't made a whit of difference in power, to me anyway. I'd rather not cut that intake, will wait until I can afford a matching AFD part and maybe trim that piece.
Be nice if Edelbrock made a single carb Air Gap, but theat might not match the TF head ports at all. TF heads usually need a TF intake to go with them.
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I thought Trick Flow made a 428/FE dual-plane...