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Building a Bowtie block 400 c.i. for my 89 IROC. Was going to go with a carb, but now having second thoughts. 3.75 stroke, 6 in rod, forged 4.125 in flat tops, 10.2 CR, AFR 195 eliminator heads. Already purchased a Comp Cams XR280R SR cam, short base circle, late model nose, 242/248 @ 0.050, .570/.576 lift, 110 lobe centerline. 106 intake centerline. Yes, I have changed the valve springs to match the SR cam. Was going to use this cam and heads with a Edelbrock air gap intake and Mighty Demon 750. Shooting for the 500 hp/500 ft-lb range for a mostly daily driver. If I go to EFI, I have a TPIS MR with 58 mm TB and 30# SVO injectors on the car now that I can use on the 400. Will probably have to up the injectors to 36 or 42#ers. I'm thinking that the MR would probably outperform the carb setup and easily get me into the hp/tq range I'm shooting for.
The big question here is should I use the Comp cam I have now? I'm a bit concerned about not having enough lobe separation for EFI. I'm in the process of asking Comp what they recommend, but as I have read on this board, the tech guys at these cam companies don't completely understand us thirdgen guys, the parts that we use, and the fact that we can tune these cars.
I should provide some additional info here to help clarify what I'm doing:
I'm going to go with an aftermarket ECM - probably BigStuff3, 3500 stall Yank TC, 700R4 Tranny, 3.73 gears.
Thanks in advance for you comments and recommendations!
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110 is doable but 112 or more is preferred.
If you run the MR then you are going to need someone who really knows their stuff as far as tuning goes because MR is a fussy intake; especially as far as fueling goes.
In last month's Popular Hot Rodding magazine, Dart did a 400 SBC that made 525/525 with a COMP HR cam, custom ground with XFI lobes, 236/242-110, .540/.540, with Dart Pro 1 Platinum 180cc heads, 1.5:1 rockers, Dart's version of the RPM AirGap, and so on, it pulled really well past 6500 rpm, all the way from 2000 rpm. It is amazing. I'm in the process of copying it for myself.
110 is doable but 112 or more is preferred.
If you run the MR then you are going to need someone who really knows their stuff as far as tuning goes because MR is a fussy intake; especially as far as fueling goes.
Thanks for the article vetteoz. Looks like the HSR is a winner to me as it clearly makes more torque and only a few less hp than the MR. Your comment about the MR being a fussy intake is the first time I've seen that. Is the HSR "fussy"? Will the HSR fit under a stock hood?
Haven't heard back yet from Comp Cams. So, I'm still thinking my current Comp cam (XR280R, part no. 12-771-8) may be okay with either the MR or the HSR. Is it worth the time and effort to put it together this way?
Looks like the HSR is a winner to me as it clearly makes more torque and only a few less hp than the MR.
I have the HSR on my worked 383 at present and are so happy with it have not bothered to swap to the MR I have on the shelf.Spins easy to limiter set @6500
Quote:
Originally Posted by CriSSes
Your comment about the MR being a fussy intake is the first time I've seen that.
Thanks again vetteoz for the reading material. Of particular interest to me was the discussion about the lean pop through the intake. I have tried to eliminate that, but was not successful with upping the AE "pump shot". I don't think I went high enough with it. I'm not sure which parameter in TunerPro RT is the best one to make this adjustment - there are 6 parameters dealing with AE. Anyone??
After reading that it is necessary to cut some of the cross bracing in the hood to use the HSR intake, I think I'll stick with the MR and try that on the 400. If I'm successful in eliminating the lean pop, I'll definitely use the MR.
Got word back from Comp Cams today on their recommendation for my 400 build. They recommended the 08-000-8 cam. It has the specs 242/248/.540/.562/HR110. Besides being a hydraulic roller, it is almost exactly the same as the 12-771-8 cam I have now - same duration, slightly less lift, and same lobe spacing. I plan to talk to Comp Cams now that they have made the recommendation to see if they agree that my solid roller cam will be equivalent and okay to use with EFI.
